594 BACTERIOLOGY. 



mal protective substance (Buchner's alexins) having no 

 specific relations to any particular variety of infection, but 

 offering some protection, more or less complete, to the 

 animal against all bacterial invasion. By the methods 

 employed in the preceding experiments it seems likely, 

 in the light of more recent work, that this normal anti- 

 dote was simply temporarily accentuated through the 

 tissue-stimulation resultant upon the treatment that the 

 animals had received, for it is not possible to bring 

 about in this way as high or as permanent a degree of 

 immunity in an animal from a particular disease as that 

 which can be obtained by the use of the specific micro- 

 organism causing the disease, or the products of its 

 growth, especially the latter. 



A striking illustration of this protective reaction on 

 the part of the animal tissues is brought out in the 

 course of R. Pfeiifer's ! experiments on Asiatic cholera. 

 He found that it is possible to confer immunity upon 

 animals from this disease; that the blood-serum of 

 such animals protects susceptible animals into which 

 it is injected against what would otherwise be a 

 fatal dose of the cholera spirillum ; that the perito- 

 neal fluid of the artificially immunized animal has 

 an almost instantaneous disintegrating (bacteriolytic), 

 bactericidal action upon living cholera spirilla that 

 are injected into the peritoneal cavity ; that the 

 serum from the immune animal, when kept for a 

 time, has no such effect upon cholera spirilla in 

 the test-tube ; but when virulent cholera spirilla are 

 injected into the peritoneum of an animal that is 



1 Pfeiffer: Zeitschrift fur Hygiene und Infektionskrankheiten, Bd. 

 xviii. S. 1 ; Bd. xx. S. 198. 



